A171581 The natural numbers without primes > 3.

1, 2, 3, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94

Offset: 1

Author

Juri-Stepan Gerasimov, Dec 12 2009, Dec 15 2009

Keywords

• nonn
• easy
• less

Comments

1, 2, 3 and the composites A002808.

Programs

Mathematica

With[{nn=100},Join[{1,2,3},Complement[Range[4,nn],Prime[Range[ PrimePi[ nn]]]]]] (* Harvey P. Dale, Nov 18 2013 *)

PARI

is(n)=if(n<5,n>0,!isprime(n)) \\ Charles R Greathouse IV, Nov 13 2015